Process for the production of alkyl aryl hydrocarbons containing a long chain alkyl group



United States Patent PROCESS FOR THE PRODUCTION OF ALKYL ARYL HYDROCARBONS CONTAINING A LONG CHAIN ALKYL GROUP George L. Hervert, Downers Grove, and Herman S.

Bloch, Chicago, Ill., assignors to Universal Oil Products Company, Des Plaines, 111., a corporation of Delaware Application October 26, 1953, Serial No. 388,372

7 Claims. (Cl. 260-671) This application is a continuation-in-part of our copending application Serial No. 119,117, filed October 1,

:1949, and now abandoned.

This invention relates to a process for the production for subsequent utilization in a sulfonation process inwhich the alkyl aromatic hydrocarbon is converted to the corresponding sulfonate having detersive qualities.

More specifically, the invention concerns a process for the alkylation of benzene utilizing long chain olefins as the alkylating agent in a process further providing for the concomitant utilization of relatively high benzene to olefin ratios and relatively high sulfuric acid catalyst to hydrocarbon charging stock ratios during the alkylation reaction.

In a continuous process for the alkylation of benzene with relatively long chain olefins containing from 9 to about 18 carbon atoms per molecule utilizing relatively concentrated sulfuric acid as the alkylation catalyst to produce alkyl aromatic hydrocarbons which upon sulfonation and neutralization of the resulting sulfonic acids yield a sulfonate product having valuable detergent properties, investigatiton of the reaction has shown that the use of sulfuric acid as the alkylating or condensing catalyst is attended by certain undesirable side reactions which adversely affect the yield of alkylate, the quantity of impurities in the alkylate product, and the desirability of the alkylate for the subsequent sulfonation reaction. At the usual operating conditions, as established by the prior art, the alkylate, for example, contains a large quantity of olefinic hydrocarbons having approximately the same boiling range as the desired alkylate product and therefore not readily separable from the latter by simple distillation. These olefins interfere with the subsequent: sulfonation of the alkylate causing high sulfonation acid consumption and correspondingly low yields of the sulfonic acid product therefrom. Furthermore, the olefins present in the alkylate product are likewise sulfonatable or sulfartable and upon reaction with sulfonating agent and neutralization yield products having a lower total detergencythan the desired alkyl benzene sulfonate individually and, in effect, reduce the quality of the ultimate detergent product. As to the elfect of the presence of the olefins on the consumption and contamination of the sulfonating acid during thesulfonation reaction, it has been observed that the olefins undergo conjunct polymerization and as a result thereof remove appreciable amounts of the sulfonating agent from the field of reactionto form a sludge-like material contaminating the ultimate sulfonic acid product. undergo oxidation in the presence of sulfonating agents such as oleum, reducing thereby the acidity of the latter,

both by consumption of sulfur trioxide and by formation of water. The sulfonation reactioninvolving the impure alkyl benzenecharging stock contaminated by the olefinic hydrocarbons therefore results in. the consumption 2,821,562 Patented Jan. 28, 1958 of a larger quantity of sulfonating agent to effect the desired sulfonation reaction, contaminates the sulfonation product with undesirable sulfates and sulfonates and dilutes the recovered sulfonating acid so that the latter cannot be conveniently recycled in the process for additional use therein. It has been found, and these observations have been made the basis of the present process, that by controlling certain process variables, as hereinafter specified, during the alkylation of benzene with olefinic alkylating agents containing from 9 to about 18 carbon atoms per molecule and utilizing sulfuric acid as the alkyl ation catalyst, an alkylate product may be obtained which is low in olefin content and which is readily sulfonatable to'produce a high yield of detergent product having superior qualities in its effectiveness as a detersive agent. It is thus one object of the invention to provide an alkylation process for producing an alkyl benzene hydrocarbon alkylate in which the content of olefinic hydrocarbon conrtaminants therein is low and which upon subsequent sulfonation yields a superior detergent product.

It is another object of the invention to provide a deter gent-forming alkylate which upon subsequent sulfonation consumes a minimum of the sulfonating agent and which produces a detergent product containing a minimum of undesired olefin hydrocarbon sulfonic acids or sulfates.

In one of its embodiments, the present invention concerns a process for the production of alkyl benzene hydrocarbons utilizing sulfuric acid as the alkylation catalyst which comprises commingling benzene with an olefinic hydrocarbon containing from 9 to about 18 carbon atoms per molecule in the presence of sulfuric acid containing less than 10% by weight of water, said process being further characterized in that the molar ratio of benzene to olefinic hydrocarbon fed to the reaction mix ture is maintained at a value of at least 3 to 1 and up to about 15 to 1, fresh sulfuric acid of at least 95% concentration is continuously supplied to the reaction mixture at a molar ratio of fresh sulfuric acid to olefinic hydrocarbon at least 1.5 to 1 to 2.0 to l, and used sulfuric acid is continuously withdrawn from the reaction mixture at a rate sufficient to maintain the ratio of total acid to total hydrocarbon at a substantially constant value.

A more specific embodiment of this invention relates to an improvement in the process for alkylating benzene with an olefinic hydrocarbon containing from 9 to ab out 1 8 carbon atoms, in which process the benzene and olefinic hydrocarbon feed stocks are continuously contracted at a temperature of from about 10 to about 50 C. with a sulfuric acid catalyst comprising a mixture of recycled, used acid catalyst and fresh make-up sulfuric acid containing less than 10% by weight of water, the improvement in Further, the olefins tend to p p said process which comprises continuously introducing said fresh acid into the alkylation process as the hydrocarbon feed stocks are introduced into the reaction and continuously withdrawing from the reaction used acid I at a rate substantially equal to the rate of adding fresh acid, while maintaining the molar ratio of benzene to olefinic hydrocarbon fed to the reaction mixture at a value of at least 3 to 1 up to 15 to l, and while maintaining a molar ratio of fresh sulfuric acid to olefinic hydrocarbon fed to the reaction mixture at a value of from 1.5 to l to 2.0 to 1.

Still other embodiments of the invention relating to process variables and other factors involved in the present alkylaztion procedure will be described in greater detail in the following further description of the invention. The combination of specific reaction conditions herein provided for the alkylation of benzene with long chain crease in the aromatic to olefinic hydrocarbon ratio when considered separately as to its influence on the yield of product, consumption of raw materials and the presence of olefinic hydrocarbons in the alkylate results in no more than a minor increase in the yield or a mere slight reduction in the olefinic hydrocarbon content of the alkylate product, while increasing the benzene consumption. Likewise, an increase in the fresh sulfuric acid to olefin ratio in the alkylation feed, when considered separately, is merely of negligible importance and does not effect an appreciable increase in the yield while likewise increasing the consumption of benzene. But when these reaction conditions are concurrently applied to a given alkylation reaction, such that both coact to produce the final alkylate product, an unexpectedly large effect is observed in that the yield of alkylate is enhanced while simultaneously the olefin content thereof is markedly reduced. The improved results are reflected in the subsequent sulfonation of the alkylate in that less sulfonating agent is required on a comparative basis to obtain a specified yield of sulfonic acid from the alkylate formed under the present reaction conditions and the product also contains a lesser amount of undesired olefin sulfonic acid and alkyl sulfate lay-products as compared with the alkylate product obtained in an alkylation reaction in which the present combination of reaction conditions is not observed. This direct relationship is believed to arise from the fact that the absence of olefins in the alkylate eliminates or greatly reduces the customary oxidation or conjunct polymerization side reactions observed when an olefinic hydrocarbon is contacted with a strong acid reagent such as a typical sulfonating agent, including concentrated sulfuric acid or an oleuln. Olefinic hydrocarbons, and particularly long chain olefins, when intimately contacted with a strong mineral acid such as sulfuric acid or oleum at the usual sulfonating temperatures of from about to about 50 C., undergo a series of hydrogen transfer and polymerization reactions, and the hydrocarbon product combines with the acid to form an acidic sludge phase, thereby, in effect, removing the acid from the sulfonation reaction and consuming the sulfonating agent to form an undesired product. At the same time, some of the olefins are oxidized to products which are likewise absorbed by the acid to form acid-soluble tars, while water and sulfur dioxide are formed as reduction products of the oleurn, thus doubly reducing the amount of oleum available for the desired sulfonation reaction. The present invention, by eliminating to a substantial degree the presence of olefins in the alkylate subsequently sulfonatcd, materially reduces the above difficulties in the production of an alkylaryl sulfonatc detergent product.

In accordance with the present alkylation procedure, benzene is alkylated with an olefinic hydrocarbon or a mixture of olefins containing from 9 to about 18 carbon atoms per molecule in the presence of sulfuric acid as alkylation catalyst by a continuous procedure in which the reactants, that is, the benzene and olefin alkylating agent, as Well as the sulfuric acid alkylation catalyst, are continuously introduced into an alkylation reactor from which the alkylate product and used sulfuric acid phase continuously withdrawn following the desired residence time in the alkylation reactor. As provided herein, the proportion of benzene to olefinic alkylating agent fed to the alkylation reactor is continuously maintained at a molar ratio of at least 3 to 1, up to about 15 to 1 during the course of the reaction, while the ratio of fresh or make-up sulfuric acid to olefin is simultaneously maintained at a molar ratio of at least 1.5 to l to about 2.0 to 1 (corresponding to a weight ratio (calculated as- 100% sulfuric acid) of acid to olefin of from about 0.9 to about 1.2). The fresh make-up acid supplied to the alkylation reaction in the present process desirably contains less than 10%, and preferably, less than about 5'%,-by weight of water, and if water is present in the hydrocarbon feed stocks or formed during the reaction, the

water content of the make-up acid is correspondingly reduced in order to maintain the water content of the acid catalyst phase in the process at less than 10% by Weight of the catalyst. The alkylation reaction is effected at temperatures of from about 10 to about 50 C., preferably from about 0 to about 30 C. with residence periods of the hydrocarbon mixture in contact with the sulfuric acid catalyst (space time factor) of from about 10 minutes to about 3 hours. In a continuous method of operation, residence or space time is a measure of the average effective length of time a particular charge of reactant remains in contact with the alkylation catalyst from the point at which the reactants are introduced into the alkylation reactor to the point at which the hydrocarbon phase is separated from the catalyst phase, and is defined as the volume of catalyst phase in the reaction zone at any time divided by the rate of flow of the hydrocarbon phase.

In order to effect this separation, the alkylate product and unreacted hydrocarbons, in admixture with the used sulfuric acid alkylation catalyst, which are usually present in the reactor as a semi-emulsion, are transferred to a settling receiver wherein phase separation occurs, the essentially hydrocarbon portion of the reaction mixture separating as an upper layer from a lower spent acid or used acid phase containing substantially all of the sulfuric acid initially charged as alkylation catalyst. According to the present process, a portion of the lower, used acid phase is withdrawn from the system at a rate of withdrawal substantially equal to the fresh acid addition rate, while the portion utilized for recycle purposes is segregated from the total stream of used acid and recharged to the alkylation zone, together with fresh or make-up acid; the amount of acid thus recycled is sufficient when combined with the fresh acid to produce a sulfuric acid catalyst phase in the reactor, containing less than 10% by weight of water and sufficient further, to provide a total hydrocarbon (olefin and benzene) to total catalyst ratio of at least 5 to 1 to about 1 to 1 by weight. An essential feature of the present process which accounts for a substantially greater yield of alkylate product of lower olefin content and a substantial reduction in the loss of benzene to the sulfuric acid catalyst phase as a result of sulfonation of the benzene and dealkylation of the product is the maintenance of the fresh sulfuric acid catalyst addition rate relative to the recycle acid addition rate within certain prescribed limits, thereby controlling the sulfonating and dealkylating activity of the catalyst phase in the reaction. As a result of extensive investigation of the process for alkylating benzene with long chain olefins in the presence of sulfuric acid alkylation catalysts, it has been found that although the exclusive use of concentrated fresh sulfuric acid as the catalyst for this alkylation reaction may result in yields of alkylate as great as or greater than those obtained when utilizing exclusively the spent or used sulfuric acid phase of a prior alkylation run, it is essential to maintain the henzene charging rate to the alkylation reaction at an exce'ssively high level in order to obtain substantial conversion of the olefinic hydrocarbon to alkylation products. Such use of high benzene to olefin ratios in the charge stock and a highly concentrated sulfuric acid catalyst, however, even at relatively low alkylation temperatures, results in a large loss of benzene to the acid catalyst phase, due to sulfonation of the benzene and the tendency of a portion of the alkylate formed as a result of condensation occurring between the benzene and do fi'nic hydrocarbons to undergo at least partial dealkylation because of the tendency of the concentrated acid to split the alkyl chain into shorter fragments. Thus, the net effect of such exclusive use of concentrated sulfuric acid as catalyst for the reaction is to reduce substantially the yield ofalkylate when such yield is based upon the benzene consumed or the amount of catalyst required and, furthermore, to produce, an alkylate product containing a relatively large proportion of undesired depolyalkylate in, which the alkyl group attached to the benzene nucleus is of shorter chain length than the olefin charged to the alkylation process.

It has now been found that if in such alkylation processes the sulfuric acid catalyst contacted with the mixture of benzene and long chain olefinic hydrocarbon is a mixture of previously used alkylation catalyst phase (i. e., recycle acid) and a certain proportion of fresh sulfuric acid (make-up acid) of at least 95% concentration, the total yield of alkylate based upon the benzene consumed is substantially greater and the quality of the alkylate product is superior than when the catalyst charged to the reaction mixture consists exclusively of fresh acid. The reason for such improved results under the present operating conditions is believed to depend upon the fact that the alkyl sulfates and sulfonic acids present in the used acid phase by virtue of its prior contact with the hydrocarbon feed stock not only inhibit the formation of additional quantities of such undesirable by-products, but also temper the activity of the fresh make-up acid by diluting it, and likewise incorporate into the catalyst phase the above-mentioned sulfated and sulfonated components having an emulsifying action on the normally hydrocarbon-insoluble acid phase and the hydrocarbon feed stock, thereby obtaining more intimate and consequently more thorough condensation of the hydrocarbon reactants. The rate of charging the fresh acid into the alkylation zone, as determined by investigation of the process to produce optimum yields of alkylate product of the highest quality, has been found to be from about 1.5 to 1 to about 2 to 1 moles of acid (as sulfuric acid) per mole of olefin. In terms of weight ratio, expressed as acid of 100% concentration and dodecyleneas an average olefin, the rate of charging fresh acid to the alkylation reactor is from about 0.9 to 1 to about 1.2 to 1 pounds of acid per pound of olefinic hydrocarbon. In view, however, of the fact that the reactivity of the catalyst with the hydrocarbon charging stocks, that is, the tendency of the acid to sulfonate the benzene and depolymerize or sulfate the olefinic hydrocarbon charge, is not only directly affected by the concentration of the acid catalyst, but is also affected by the molecular weight of the olefin and the ratio of benzene to olefin charged to the reaction, the simplest means of expressing the fresh acid addition rate, which means accounts for the effect of the above factors on the principal and side reactions, is on the basis of molar ratios. The fresh acid may be sulfuric acid of any concentration greater than about 95% by weight of acid, up to 100% concentration, and the particular concentration utilized in any given alkylation process depends upon the concentration of sulfuric acid in the recycle acid stream, the fresh or make-up acid being sufliciently concentrated to reduce the water content of the acid catalyst phase in the alkylation zone, after mixing with the recycle acid, to less than by weight of water, based on the catalyst composite.

1n thepresent continuous method of alkylation the spent acid (a portion of which is recycle acid) is continuously separated from the hydrocarbon alkylate product in-a receiver or settling vessel, as aforesaid. The

upper hydrocarbon phase thus separating in the receiver, may, if desired, be washed with water to remove any en- .trained sulfuric acid catalyst prior to fractional distillation to separate the desired alkylate product from unconverted reactants. The alkylate fraction, which boils at a temperature of from about 230 to about 400 C. (depending upon the molecular weight of the olefinic alkylating agent utilized in the process) is removed as a 1 separate fraction and reserved for subsequent sulfonation, while 'the unconverted olefinic hydrocarbon reactant, if any, intermediate fractions and benzene are separated and the benzene recycled to the alkylation reaction vessel, if desired. It is found that the alkylate fraction separated as a distillate cut is substantially free of olefinic hydrocarbons.

The benefit of utilizing a'combination of benzene to olefin molar ratios of at least 3 to 1, up to about 15 to 1 and fresh acid to olefin molar ratios of'from 1.5 to l to 2 to 1 is illustrated graphically in the accompanying diagram wherein the data, based upon experimental ob servation, illustrate thatunder the preferred operating conditions herein provided a definite criticality is established in the yield of alkylate per unit weight of olefin alkylating agent charged to the alkylation reaction. This yield expressed in the above units when utilizing ratios of fresh acid to olefin of less than 1.5 to 1 molar proportions (e. g. 1 to l) is not characterized by any required critical minimum proportion of aromatic to olefins in the charging stock; rather, the yield merely increases gradually as the benzene/olefin ratio charged increases and the yield increase approaches a maximum which is considerably less than the yields realized from the reaction when the ratio of acid to olefin is from 1.5 to 2.0 moles of acid per mole of olefin.

The benzene reactant herein provided for the present alkylation. reaction may comprise substantially pure benzene, although hydrocarbon fractions containing benzene, such as a suitably boiling fraction separated from the products of a pyrolytic petroleum cracking reaction or from a catalytic dehydrocyclization reaction, preferably olefin-free and containing at least 70% by weight of benzene, may likewise be utilized in the present alkylation process. Such benzene-containing fractions in which the benzene content is generally greater than about 35% by weight thereof which may be utilized as the source of benzene reactant in the present process are conveniently recovered as separate fractions from the gasoline boiling range material of petroleum refining processes or from straight-run or natural gasoline.

The olefinic hydrocarbon alkylating agent employed in the present alkylation reaction, as heretofore specified, contains olefins having from 9 to about 18 carbon atoms per molecule, which may be charged as a mixture of olefinic components having the above molecular chain lengths or as a substantially pure individual component. Olefinic hydrocarbons of the above characteristics may be obtained from any suitable source but are most conveniently derived from the olefinic fractions of thermally cracked petroleum products boiling from about to about 300 C., particularly those boiling in the range of from about C. to about 225 C., or from certain olefinic polymer products formed by the catalytic or thermal polymerization of lower molecular weight monomers, such as olefin monomers containing from about 2 to about 4 carbon atoms per molecule.

One of the preferred sources of such olefinic polymer alkylating agents is the product formed by the polymerization of propylene over a solid phosphoric acid catalyst (a kieselguhr-phosphoric acid composite) and separating from the total polymer product a fraction containing components having from 9 to about 18 carbon atoms.

Another source of olefins suitable for the present process comprises olefinic fractions formed by the dehydrochlorination of monochlorinated kerosene boiling within the range of about 130 to about 300 C.

The alkylation catalyst utilized herein to effect the condensation of benzene with the olefinic alkylating agent is specified as a mixture of fresh sulfuric acid and previously used, recycle acid recovered from a prior alkylation run and containing not more than 10% by weight thereof of water, and preferably not more than about 5% by weight of water. The portion of used catalyst separating from the hydrocarbon product in the settling receiver following the alkylation reactor is, in accordance with the present process, continuously mixed with the fresh sulfuric acid catalyst to form a mixture of used and fresh acid, the water content of which is not greater than 10% by weight, the resulting mixture being charged continuously into the alkylation reactor to contact an additional charge of benzene and olefinic alkylating agent. The withdrawn portion of the acid which is not recycled may be redistilled or otherwise treated to separate the concentrated acid therefrom which may be utilized as fresh make-up acid.

The alkylation reaction is desirably conducted in a kettle or other reactor in which the contents may be stirred or otherwise agitated to intimately mix the catalyst with the reactants. In the present continuous type of alkylation reaction, the reactor may consist of a tubular vessel of sufiicient size to permit the desired residence or space time of the hydrocarbon reactants with the catalyst at the particular flow rate provided, the hydrocarbon reactants and sulfuric acid being introduced into one end of the reactor, thereafter vigorously stirred therein and ultimately Withdrawn, following the required residence time, from the discharge end of the tube.

The invention is further illustrated with reference to specific embodiments thereof and for the purpose of demonstrating the advantages of the present method of operation, in the following example which, however, is not intended to unduly restrict the generally broad scope of the invention in strict accordance thereto.

EXAMPLE In the following experiments, various aromatic hydrocarbon to olefin hydrocarbon molar ratios and various fresh sulfuric acid to olefin ratios were utilized in a series of continuous alkylation runs to determine the independent and combined effect of these variables on the yield of alkylate product and upon the olefin content of the alkylate fraction separated from the products of the alkylation reaction mixture. Each of the alkylation reactions involves the alkylation of the benzene component of a benzene-containing fraction concentrated from a straight-run gasoline and containing approximately 70% by weight of benzene with an olefinic hydrocarbon fraction boiling from about 170 to about 225 C. formed by the polymerization of propylene over a solid phosphoric acid polymerization catalyst. The alkylation is effected on a continuous basis by contacting a mixture of the benzene concentrate and the above described propylene polymers with a mixture of recycled sulfuric acid alkylation catalyst from a prior continuous alkylation run with sufficient 98.6% sulfuric acid to maintain the volume ratio of total hydrocarbon to total acid in the reactor at 3 while providing a predetermined molar ratio of fresh acid to olefinic hydrocarbon in the reactor. A continuous process was provided by continuously charging the mixture of hydrocarbons and mixed fresh and recycled alkylation catalyst into a well-stirred cooled autoclave and continuously Withdrawing a mixture of hydrocarbons and used sulfuric acid alkylation catalyst from the reactor, allowing the withdrawn mixture to settle, and thereafter separating an acid phase from the upper layer hydrocarbon phase. A portion of the used acid phase from the settling vessel approximately equal in amount to the fresh addition acid was withdrawn continuously from the spent acid phase, analyzed to determine the composition of the recycle acid, and discarded from the process, thereby maintaining the ratio of total acid to total hydrocarbon constant in any given alkylation run. The remainder of the used acid was mixed with fresh 98.6% sulfuric acid to provide the indicated hydrocarbon to acid ratio and the resulting mixture charged continuously with the fresh benzene and olefinic hydrocarbon reactants into the alkylation reactor. The upper hydrocarbon phase withdrawn from the settling vessel was continuously fractionated, benzene being continuously withdrawn overhead for recycle, a side-cut of intermediate boiling range hydro-carbons being continuously withdrawn and discarded, and the column bottoms being transferred to another column and distilled under vacuum to recover a 275-345 C. fraction as the alkylate product.

USING 98.6% lH'AKE-UP SULFURIC ACID IN A CONTIN- U0 US PROCESS Run N o I II III IV V Operating Conditions:

Aromatic/Olefin (mols) 1.5 4. 5 1. 5 4.5 9.7 Hydrocarbon/Acid (vol.) 3. 01 3.19 3.09 3.01 2.0 Lbs. of fresh 98.6%/Lb. Olifln- 1.16 0.614 0.59 1.22 1.02 Moles of iresh Acid/Mole Olefin 1.03 1.0 2. 00 1.7 Temperature, 0.. 3 3 3 3 3 Space Time, Min 38. 9 38. 3 39. 9 63.2 Acid Phase Analysis:

Total Acidity, as Wt. percent H 504 83. 6 77. 2 79. 5 83.3 Total Water, Wt. percent 7. 6 6.5 7.8 7. Yields:

Alkylate (275345 0.), Lbs./

lb. of Olefin 0. 572 0.720 0. 517 0.875 0. 846 Alkylate, percent theoretical,

based upon olefin .t 39.1 48. 7 35. 5 59. 8 58. 0 Pro erties of Alkylate:

romine number 6.8 5.2 7.5 1.5 1.2

l Determined as titratable acidity, including acid sulphates and sulphonic acids.

2 Index of olefin content-centigrams 0t bromine per gram of sample.

The above results indicate that only when an aromatic to olefin molar ratio greater than 3 and a fresh acid to olefin molar ratio greater than 1.5 moles of acid per mole of olefin are utilized simultaneously in a given alkylation reaction does the desired alkylate contain a low concentration of olefins and is a high yield of alkylate per weight of the olefin charged obtained. The results further indicate that when each of the above factors is applied separately, that is, a high aromatic to olefin ratio is utilized in the reaction, in the absence of the high acid to olefin ratio (run II compared with III), or a high acid to olefin ratio in the absence of a high aromatic to olefin ratio (run I compared with run III), the desired yield of alkylate product containing a low concentration of olefinic hydrocarbons in the alkylate product is not obtained. Thus, when the aromatic/ olefin mole ratio charged to the reaction is 1.5 (below the desired 3 to 1 ratio) and although the fresh acid addition rate is high (1.97 moles of acid per mole of olefin), the yield is substantially less (39.1% of theoretical) than when a high aromatic to olefin ratio, combined with a high fresh acid addition rate, are concurrently utilized in the reaction (59.8% of theoretical yield). Similarly, a high aromatic to olefin ratio when utilized independently in the reaction at a low fresh acid addition rate, results in a low yield of alkylate product (48.7% of theoretical) compared with the aforementioned reaction wherein both the fresh acid addition rate and the aromatic to olefin ratio is high.

We claim as our invention:

1. In a continuous process for the production of an alkylbenzene hydrocarbon which comprises commingling benzene with an olefinic hydrocarbon containing from about 9 to about 18 carbon atoms per molecule in the presence of sulfuric acid containing less than 10% by weight of water, the improvement in said process which comprises maintaining the molecular ratio of benzene to olefinic hydrocarbon fed to the reaction mixture from 3 to l to about 15 to 1, continuously introducing fresh sulfuric acid of at least concentration into the reaction mixture at a rate sufficient to maintain the molar ratio of fresh sulfuric acid to olefinic hydrocarbons fed from 1.5 to 1 to 2 to 1 and continuously withdrawing from the reaction mixture used sulfuric acid at a rate sufiicient to maintain the ratio of total acid to total hydrocarbon at a substantially constant value.

2. The process of claim 1 further characterized in that said olefinic hydrocarbon is an olefinic hydrocarbon fraction boiling from 170 to 225 C.

3. The process of claim 2 further characterized in that said olefinic fraction is a propylene polymer.

4. The process of claim 1 further characterized in that said process is eflFected at a temperature of from about to about 30 C.

5. The process of claim 1 further characterized in that the total hydrocarbon to total acid weight ratio is maintained in the reaction mixture at from about 5 to 1 to about 1 to 1.

6. The process of claim 1 further characterized in that said benzene is supplied to the reaction mixture in the form of a paraflinic hydrocarbon-benzene mixture containing at least 35% by weight of benzene.

7. In an improved process for alkylating benzene with an olefinic hydrocarbon containing from 9 to about 18 carbon atoms, in which process the benzene and olefinic hydrocarbons are continuously contacted at a temperature of from about 10 to about 50 C. with a sulfuric acid catalyst comprising a mixture of recycled, used sulfuric acid catalyst and fresh, make-up sulfuric acid, said mixture containing less than 10% by weight of water, the improvement in said process which comprises continuously introducing said fresh acid into the alkylation process as the hydrocarbon feed stocks are introduced into the reaction and continuously withdrawing from the reaction used sulfuric acid at a rate substantially equal to the rate of adding said fresh sulfuric acid, while maintaining the molar ratio of benzene to olefinic hydrocarbon fed to the reaction mixture at from 3 to 1 to to 1, and while maintaining a molar ratio of fresh sulfuric acid to olefinic hydrocarbon fed to the reaction mixture at a value of from 1.5 to1to2to1.

References Cited in the file of this patent UNITED STATES PATENTS 2,439,457 Donleavy et a1 Apr. 13, 1948 2,567,854 Nixon Sept. 11, 1951 2,718,526 Mammen Sept. 20, 1955 

1. IN A CONTINUOUS PROCESS FOR THE PRODUCTION OF AN ALKYLBENZENE HYDROCARBON WHICH COMPRISES COMMINGLING BENZENE WITH AN OLEFINIC HYDROCARBON CONTAINING FROM ABOUT 9 TO ABOUT 18 CARBON ATOMS PER MOLECULE IN THE PRESENCE OF SULFURIC ACID CONTAINING LESS THAN 10% BY WEIGHT OF WATER, THE IMPROVEMENT IN SAID PROCESS WHICH COMPRISES MAINTAINING THE MOLECULAR RATIO OF BENZENE TO OLEFINIC HYDROCARBON FED TO THE REACTION MIXTURE FROM 3 TO 1 TO ABOUT 15 TO 1, CONTINUOUSLY INTRODUCING FRESH SULFURIC ACID OF AT LEAST 95% CONCENTRATION INTO THE REAC- 